The UC Davis Cancer Center Mouse Biology (MB) shared resource is one of the original Cores initially established by the first CCSG submission. When first reviewed, the newly conceived and created MB shared resource received a rating score of outstanding and several laudable comments from CCSG reviewers. Building upon that earlier success, and recognizing the essential importance of inducant mutations in the mouse genome to advances in research on the biology, diagnosis, treatment, and prevention of cancer in humans, the MB shared resource continues to be a critically integral component of the research mission of the Cancer Center. Utilizing the wide breadth and depth of expertise and infrastructure of the UC Davis Mouse Biology Program, this Core serves and supports cancer-related research by cancer center members utilizing genetically-altered mice. The Core provides all of the necessary technical elements for de novo creation and derivation of transgenic, knockout, and other types of induced mutant mice, husbandry, maintenance, health-care, and well-being of mice, and an extensive array of genotyping and phenotyping capabilities and services to Cancer Center members on a prioritized basis and at a subsidized cost. In addition. Core leadership faculty and their associates contribute intellectually to the development of research areas and projects by Cancer Center members who incorporate genetically altered mice into their research. Since its inception, the success of this Core to the overall mission of the Cancer Center is immediately evident by noting the accomplishments of the 32 Cancer Center members requesting more than 1300 Core services in support of their cancer-related research during the first 3 years of the CCSG. In this competitive renewal, the Core intends to continue to offer superior technical excellence and scientific input in anticipation ofan increasing number of requests from Cancer Center members during the next 5 years. The specific aims of the MB shared resource are divided into 3 principal service categories: 1) Mouse Model Creation Services; 2) Mouse Husbandry and Maintenance Services; and 3) Mouse Genotyping and Phenotyping Services .